My weekday birding is usually limited to a quick dash from my office building out to the northwest corner of Lake Merritt. Two or three times during the last couple of weeks a hummingbird has caught my eye as being "different", but I couldn't say why. However, since I have seen an Anna's Hummingbird almost everyday in the last four months, I've got a good feel for what is normal.
Today I was able to get a good look at the stranger. Field marks include: green back, white underside, no notable coloring on chin or neck, longish bill curved downward somewhat, a white spot behind the eye, a dark stripe from the base of the bill to the front of the eye, and wings that extend beyond the tail when perched.
I have only seen a Black-chinned Hummingbird twice, both males, one in the San Joaquin Valley and one in the foothills of the Sierra Nevada. Do they occur in the bay area? Do I need to note any other field marks to be more certain of the identity?
I appreciate any help or advice you can give.